GDBus.Error:org.freedesktop.DBus.Error.InvalidArgs: Logical monitors not adjacent

[peteruithoven]

What Happened?

I've just ran some updates for elementary OS and my display configuration seems to have been forgotten. When I opened Display settings the displays in the layout overlap:

When trying to apply a alternative layout I'm getting the following error:

GDBus.Error:org.freedesktop.DBus.Error.InvalidArgs: Logical monitors not adjacent

Settings of build in laptop screen:

Settings of external monitor:

I've tried multiple layouts:

I've also noticed a lot of applications seem to open up way bigger, maybe twice as big. So this might be a Gala issue. (Also see: elementary/gala#2671)

Steps to Reproduce

1. Open display settings
2. Adjust layout (just placement, no other settings resolution, scaling factor etc)
3. Press Apply

Expected Behavior

I can adjust displays layout.

OS Version

8.x (Circe)

OS Architecture

amd64 (on most hardwares)

Session Type

Secure Session (Wayland)

Software Version

Latest release (I have run all updates)

Log Output

Opening settings from the terminal shows:

(io.elementary.settings:10766): io.elementary.settings.display-CRITICAL **: 12:23:52.535: display_displays_overlay_show_windows: assertion 'gala_dbus != null' failed

(io.elementary.settings:10766): io.elementary.settings.display-CRITICAL **: 12:23:52.536: display_displays_overlay_show_windows: assertion 'gala_dbus != null' failed

Hardware Info

• Laptop: Framework 15
  • AMD Ryzen™ AI 300 Series
  • Screen: 2880x1920 120Hz
• External monitor: Dell P2415Q
  • 24"
  • 3840×2160

[peteruithoven]

Possibly related: #435

[marmeladapk]

I also have this problem since last update. For me, with laptop screen+external monitor I can't put the external monitor on the right or on the bottom of the laptop screen, however left or over is accepted. Possibly related to recent fractional scaling updates? Laptop screen is at 175%, external monitor at 100%.

[peteruithoven]

For anyone else please see leolost2605's temporary fix:
elementary/gala#2691 (comment)

[lobre]

Hey, adding some extra context here in case it helps.

I’m hitting the same GDBus.Error: Logical monitors not adjacent error, and it seems closely tied to scale-monitor-framebuffer being enabled (which is now the default on elementary). When that feature is on, Mutter switches to logical layout mode (needed for fractional scaling).

What seems to happen is:

• The display layout UI lets you position monitors in a way that looks valid
• But when applying the configuration, Mutter rejects it because the logical monitor rectangles aren’t perfectly adjacent
• Disabling scale-monitor-framebuffer makes the problem go away entirely

My suspicion is that settings-display is computing or adjusting monitor positions assuming physical pixel sizes, while Mutter expects logical coordinates when logical mode is active. That would explain why layouts that look aligned end up being rejected.

This also lines up with some side effects like apps suddenly appearing much larger after updates, which seems to happen around the same time this layout issue shows up.

[lobre]

I spent a bit of time comparing how this is handled in settings-display vs GNOME’s display panel (gnome-control-center), and it looks like the core issue is how layout geometry is handled when Mutter is in logical layout mode (scale-monitor-framebuffer).

In GNOME, once layout-mode is logical, all layout and snapping math is done in logical coordinates, not raw mode pixels. So, the UI rectangles used for alignment/snapping are derived as round(mode_size / scale) (with rotation applied after), and snapping/adjacency is enforced using those logical sizes. That way, what the UI considers "touching" is exactly what Mutter later validates.

In settings-display, it seems that:

• x/y come from Mutter logical monitors (so they’re already logical),
• but the widget sizes used for layout/snapping still come from raw mode width/height (physical pixels),
• which means the overlay ends up mixing logical positions with physical sizes.

With fractional scales, that mismatch can easily produce tiny logical gaps after Mutter recomputes logical sizes internally, which then triggers the "Logical monitors not adjacent" error even though the layout looks fine in the UI...